The dental and medical clinicians of the Clinical/Laboratory Core will see all patients referred by the San Francisco epidemiology cohorts and validate diagnoses. From these referrals and other sources of patient referrals, they will continue to build clinical cohorts of patients with specific oral lesions in order to analyze their relationship to the development of AIDS and to other markers/predictors. They will obtain biopsies and other samples for the studies in Projects 2, 3, and 4 from well-characterized patients with the oral lesions being studied. The core staff will be responsible for clinical research patient records, for specimen handling and storage and for getting specimens to Project 2, 3, and 4 investigators. They will stain smears and sections, handle samples and biopsy tissue specimens, process blood specimens, maintain pathology and other clinical laboratory data, perform in situ hybridization for Epstein-Barr virus to confirm the diagnosis of hairy leukoplakia. The Clinical/Laboratory Core investigates will continues will continue to study the clinical and pathological features of the oral manifestations of HIV infection and, in conjunction with Project 1, 2, 3, and 4 investigators, will continue to report new features and to explore their etiology, pathogenesis, responsive to therapy, and host immune response to oral pathogens. Part of the responsibilities of the investigators in the Cores and the Projects will be to continue to document and publish such findings and to conceive and test new hypothesis concerning this fascinating and challenging group of diseases.